feat: Push als Chat-Verlauf - mehrere Nachrichten, voller Text, Bildvorschau, echtes "Gelesen"

Bernds Beta-Feedback: pro Raum wurde jede Nachricht durch die naechste ersetzt
und auf 100 Zeichen gekuerzt, ohne Bild. Jetzt:
- NotificationHelper: MessagingStyle mit den letzten 8 Nachrichten pro Raum
  (Verlauf in SharedPreferences, nur solange die Benachrichtigung sichtbar ist),
  gleiche eventId ersetzt (Platzhalter -> Klartext), nur Neues klingelt.
- notification_content.dart: Text bis 1000 Zeichen, Antwort-Zitat entfernt,
  Medien-Labels, Vorschau-Einstellung auch bei gekillter App; Bild (E2EE
  entschluesselt) + Avatar per FileProvider an die System-UI.
- "Gelesen" setzt eine echte Lesebestaetigung (Haupt-Engine bzw. BgEngine).
- Laufende App holt genau das gepushte Event statt room.lastEvent.
- Debug-only DebugNotifyReceiver zum Testen per adb ohne Login.
Emulator (API 36): Verlauf, Ersetzen, Bild, Avatar, Gelesen geprueft;
9 neue Tests. Echtes Geraet (Bernd) steht aus.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

lib/core/background_push.dart

@@ -8,6 +8,7 @@ import 'package:flutter_local_notifications/flutter_local_notifications.dart';
 import 'package:flutter_vodozemac/flutter_vodozemac.dart' as vod;
 import 'package:matrix/matrix.dart';
 import 'package:pyramid/core/app_database.dart';
+import 'package:pyramid/core/notification_content.dart';
 import 'package:pyramid/core/soft_logout_guard.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
@@ -64,6 +65,11 @@ void notificationEngineMain() {
             args['room_id'] as String?,
             args['text'] as String?,
           );
+        case 'markRead':
+          return await _bgMarkRead(
+            args['room_id'] as String?,
+            args['event_id'] as String?,
+          );
       }
     } catch (e) {
       debugPrint('[NOTIF-BGENGINE] handler error: $e');
@@ -88,26 +94,27 @@ Future<bool> _bgDecryptAndShow(String? roomId, String? eventId, int? notifId) as
         )
         .timeout(const Duration(seconds: 20));
     if (event == null) return false;
-    // Bad-encrypted body still starts with "**" — keep the native placeholder.
-    if (event.body.startsWith('**')) return false;
 
-    final room = client.getRoomById(roomId);
-    final sender = room?.unsafeGetUserFromMemoryOrFallback(event.senderId).displayName ??
-        event.senderId.split(':').first.replaceFirst('@', '');
-    final title = (room?.isDirectChat ?? true)
-        ? sender
-        : '$sender · ${room?.getLocalizedDisplayname() ?? ''}';
+    final prefs = await SharedPreferences.getInstance();
+    final content = MessageNotificationContent.fromEvent(
+      event,
+      showPreview: prefs.getBool('notif_preview') ?? true,
+    );
+    // Nicht entschlüsselt / nichts Anzeigbares → nativer Platzhalter bleibt.
+    if (content == null) return false;
 
     // Hand the decrypted content back to native so it re-shows the SAME
     // notification via NotificationHelper — that keeps the reliable
-    // MainActivity-based reply action (the flutter_local_notifications reply
-    // path doesn't fire dependably when the app is killed).
-    await const MethodChannel(_kBgEngineChannel).invokeMethod('showDecrypted', {
-      'title':    title,
-      'body':     _buildBody(event),
-      'room_id':  roomId,
-      'notif_id': notifId ?? _stableId(roomId),
-    });
+    // ReplyReceiver-based reply action (the flutter_local_notifications reply
+    // path doesn't fire dependably when the app is killed). Erst der Text,
+    // dann lautlos Avatar/Bild (deliverMessageNotification).
+    await deliverMessageNotification(
+      event,
+      content,
+      notifId: notifId ?? _stableId(roomId),
+      send: (a) => const MethodChannel(_kBgEngineChannel)
+          .invokeMethod('showDecrypted', a),
+    );
     return true;
   } catch (e) {
     debugPrint('[NOTIF-BGENGINE] decryptAndShow error: $e');
@@ -152,6 +159,27 @@ Future<bool> _bgSendReply(String? roomId, String? text) async {
   }
 }
 
+/// „Gelesen“ bei beendeter App: Lesebestätigung bis [eventId] setzen (reiner
+/// HTTP-Aufruf, keine Verschlüsselung nötig).
+Future<bool> _bgMarkRead(String? roomId, String? eventId) async {
+  if (roomId == null || eventId == null) return false;
+  final client = await _buildClient();
+  if (client == null) return false;
+  try {
+    final room = client.getRoomById(roomId) ?? Room(id: roomId, client: client);
+    await room
+        .setReadMarker(eventId, mRead: eventId)
+        .timeout(const Duration(seconds: 15));
+    debugPrint('[NOTIF-BGENGINE] read marker set for $roomId');
+    return true;
+  } catch (e) {
+    debugPrint('[NOTIF-BGENGINE] markRead error: $e');
+    return false;
+  } finally {
+    await client.dispose().catchError((_) {});
+  }
+}
+
 /// Stores the raw callback handle of [notificationEngineMain] so native code can
 /// bootstrap the background engine. Call once at app startup.
 Future<void> registerBgEngineHandle() async {
@@ -217,20 +245,6 @@ Future<Client?> _buildClient() async {
   }
 }
 
-String _buildBody(Event event) {
-  final msgType = event.messageType;
-  final rawBody = event.body;
-  return switch (msgType) {
-    'm.text'    => rawBody.length > 100 ? '${rawBody.substring(0, 100)}…' : rawBody,
-    'm.image'   => '📷 Bild',
-    'm.video'   => '🎥 Video',
-    'm.audio'   => '🎵 Audio',
-    'm.file'    => '📄 Datei',
-    'm.sticker' => '🏷️ Sticker',
-    _           => rawBody.isEmpty ? 'Neue Nachricht' : (rawBody.length > 100 ? '${rawBody.substring(0, 100)}…' : rawBody),
-  };
-}
-
 // ── Notification action handler ───────────────────────────────────────────────
 // Called in a fresh Dart isolate when the user presses Reply or Gelesen.
 // Must return quickly — Android keeps the notification's "sending" spinner